High frequency directive beam apparatus



Oct. 22, 1957 E. J. BARLoW HIGH FREQUENCY DIRECTIVE BRAM APPARATUS 3 Sheets-Sheet 1 Filed Aug. 23. 1949 IIIJ ATTORNEY NNN www

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HIGH FREQUENCY DIRECTIVE BEAM APPARATUS Filed Aug. 23, 1949 3 Sheets-Sheet 2 rl/NING :E

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ATTORNEY IOcLIZAZ, 1957 E. J. BARLOW A 2,810,905 l v n HIGH FREQUENCY DIRECTIVE BEAM APPARATUS Filledv Aug. 23. 1949 E Y ATTORNEY Y 2,810,905v i y y HIGH FREQUENCY DIRECTIVE BEAM APPARATUS v Edward J. Barlow, Pacfi Palisades,V Calif., asslgndr to Sperry Rand Corporation, acorporation of Delaware Application August 23, 1949, Serial No.' 111,799

zo claims. A (cl. 34a- 100) The present invention relates to directive beam systems for microwave energy, and is concerned especially with the provision of an antenna arrangement for rproviding a directive pattern varying or shifting in a predetermined relation with frequency of the energy emitted or received thereby. f Y

An object of this invention is to provide an antenna system for the generation of apredetermined directive pattern, and for enabling the effective swinging of the directive pattern according to variation of supplied frequency.

Another object of the present invention is to provide an arrangement for variable reflection of electromagnetic energy in accordance with frequency thereof.

A further object is to provide a rotatable antenna system arranged for operation at a plurality of input'frequcncies and for provision of a plurality of directive patterns at a series of different angles relative to the axis ,of rotation, the moment `of inertia of the rotatable system being kept to a minimum. l Y l n These objects are accomplished'and further features are made possible through the userof an energy reflecting system designed as a waveguide'or a lgroup of Ywave guides, each guide having different progressively narrower cross sectional widths of the interior space at progressively greater depths therein, and being so arranged that when energy of a plurality of frequencies or of varied frequency is introduced into the mouth of the Wave guide, the energy components of the lower frequencies can be efliciently conducted only to a relatively shallow depth in the wave guide whereas energy components of progressively higher frequencies and shorter wavelengths are efficiently conducted to greater depths within the wave guide.

This wave guide system acts with respect Vto an energy component of a given frequency substantially as though there` were provided a metallic reflecting sheet at that depth in the Wave guide beyond which the energy cannot be efficiently propagated, i. e. at that depth at which the Wave guide width or wall spacing dimension is substantially the cut-off dimension for a Wave guide with respect to the frequency of the given energy component. The wave guide for providing this feature may be tapered gradually from maximum inter-walls spacingat the energy entrance region to minimum spacing at the rear, or it may be provided with minute steps in the Walls, delineating abrupt changes in the spacing 'between wall sections.

Frequency changes of the order of 1% or 2%, or as great as may be employed for changing from one reflection region to another, where step scanning is to be achieved. A plurality of similar wave guide units with substantially identical stepped or smoothly tapered walls may be placed side by side to achieve appreciable breadth of the energy reflecting regions. For example, for an effective aperture width of the order -of fifteen wavelengths, the number of similar wave guides placed side by side may be of the order of thirty to fifty units.

- Further objects and features ofthe present invention will be made apparentin the ensuing description of select-` Patented Oct. 212, 1957 ed embodiments of the invention illustrated in the a'ccompanying drawings, wherein:

Fig. 1 is a sideelevation view, partly schematic, of a radar system arranged for continuous rotation about a vertical axis, and for the generation of a series of'cigarshaped directive patterns at a series of different angles of elevation; v

Fig. 2 is a front elevation view of the cut-oifwave guide reflector array, in an embodiment with vsteps formed in the walls therein;

Fig. 3 is a front elevation view of a modification with smooth tapers of the wave guide sections;

Fig. 4 is a side elevation of a wave guide reflector system formed with steps executed according to parabolic section curves, so arranged as to effect partial collimation of the energy introduced into the wave guide;

Fig. 5 is an oblique View of a modification of the system of Fig. 4, incorporating the features of electromagnetic lens contours in the lower edge projections of the wave guide walls; and

Fig. 6 illustrates a modified version corresponding to Fig. l, wherein the lower edges of the multiple wave guide walls are made to conform to a Fresnel-type lens, for fully collimating energy radiated from the focal point of the lens.

The radar system illustrated in Fig. l comprises a vertically directed paraboloidal reflector 11 arranged to be excited by a dual dipole exciter unit 13. Unit 13 comprises a pair of dipoles spaced approximately one fourth wavelength apart and energized by energy supplied from the mouth of a wave guide 15, the dipole` elements being mounted in a perpendicular plate 17 attached to the waveguide 15. These dipoles are located substantially vat the focal point of the paraboloidal reflector 11,` and in this arrangement, energy supplied to them through wave guide 15 is radiated principally toward the paraboloidal reflector 11. Y

A radar transmitting and receiving system is coupled to the Wave guide 15 and arranged for supplying high power energy pulses to the antenna elements 13 for ultimate transmission in a concentrated beam, and for receiving weak pulses of energy reflected back from remote objects. This radar system is -conventional in most respects, but is arranged to operate over a plurality of frequencies, either by continuous frequency sweeping as by motor control of the radar transmitter and receiver tuning or by discrete steps in frequency, which may be of the order of 2% frequency changes, the frequency steps being preferable. ator and one receiver unit can be arranged to be tuned to successive different frequencies, Fig. 1 for simplicity indicates the use of separate transmitter-receiver units 19, 21, 23, 2.5, 27 and 29, one for each of six operating frequencies.

These transmitter-receiver units may each be arranged for transmission of approximately 1000 pulses per second the pulse duration being of the order of one microsecond, with the reecivers arranged to detect the weak reflected energy pulses arriving at intervals after pulse transmissions corresponding to the distances of the energy reflecting obiect or objects. If desired, moreover,the radar transmitter-receiver units may be intercoupled with timingV links 31, 33, 35, 37 and 39, for successivelyv triggering the transmitter-receiver units in timed relation to the transmission from the first unit 19. Link 31, for example, may be arranged to convey from unit 19 to unit 21a version of the blocking oscillator impulses provided by the timing pulse generator in unit, V19, for triggering the pulse generator in unit 21 shortly thereafter. Any desired `amount of time delay may be provided in these coupling links, as by the use of well known variabledelaylines therein.

A multiple wave guidevarray arranged asa variable;

Although one radio frequency generav reflecting system 40 is provided directly above the anl tenna system 11, 13, for receiving the collimated energy beam therefrom and for reilecting the various frequency components therein at various predetermined angles of elevation. The reflector system 40 is so arranged as to provide an effective reflection plane at an inclination slightly higher than 45 for the energy of .frequency f1 supplied by the radar transmitter-receiver unit 19, this rellection plane being seen in edge view at 41. The array 40 provides a different reflection plane for the slightly higher frequency f2 at which radar transmitter-receiver unit 21 operates, this plane being seen in edge view at 43. Similar reflection planes at'45, 47, 49 and 51 are effective for the successively higher frequencies f3, f4, fs and fe of radar units 23, 2S, 27 and 29, respectively, as will hereafter be brought out more fully. Y

The eifective reflection planes for the successively higher frequencies are provided at successively steeper inclinations, in order that the directive lobes for the respective radar units will be aimed at successively higher angles of inclination, providing the same effect as though a battery of several conventional paraboloidal reflector antenna units were arranged in a cluster, and aimed in parallel vertical planes but at successively higher angles of inclination, one such complete paraboloidal antenna system being provided for each of the several radar units.

The rellector system 40 is supported for rotation about the directive axis of the paraboloidal reflector 11, as by a set of flanged wheels such as wheels 50, 52, 53, 54 and 55 arranged on radially extending spokes and riding upon a circular track 56. This rellector structure 40 is coupled as by a ring gear 57 on the outwardvextension of these spokes and a spur gear 59 in mesh therewith to a scanner azimuth drive motor 61, for regular rotation of the system in azimuth. The dual dipole system 13 is mechanically coupled to the reflector system 40 for rotation therewith, so that the dipole elements are always parallel with the sides of the reflector system 40.

The reilector unit 40 comprises a plurality of similar wave guide units arranged side by side as illustrated in front elevation in Fig. 2 or Fig. 3, with stepped or tapered interior wall congurations for providing the different reflecting zones for the respective radar unit frequencies. The stepped wave guide array in Fig. 2 comprises seven identical wave guide units placed side by side, with their lower side boundaries contiguous; these wave guide units are designated 63, 65, 67, 69, 71, 73 and 75. Unit 63, typical of all seven units in this assembly, comprises an inclined metal back plate 77, a vertical lower back plate 79 and a vertical metal sheet system providing diagonally extending interior steps. The widest spaced plate sections 81 and 83 are adjacent the microwave energy entrance grid at the bottom of the array, and are spaced apart suiliciently for efhcient transmission of microwave energy of the frequency f1 generated and received by radar unit 19, as well as energy of all of the higher frequencies of units 21, 23, 25, 27 and 29. The next section of wave guide unit 63, with parallel interior wall sections designated 85 and 87, is characterized by a slightly smaller separation dimension, so that the wave guide section cornprising these two metallic sheet sections is incapable of transmitting energy of the frequency f1 generated and received by radar unit 19, but is readily capable of transmitting the frequency f2 of radar unit 21 and the higher frequencies of units 23, 25, 27 and 29.

The next parallel plate wall sections 89 and 91 constitute a still further wave guide section which is cut off for energy of the frequencies of radar units 19 and 21, but which transmits the frequency f3 of unit 23 and tne higher frequencies of units 25, 27 and 29. Similarly, wave guide section 93, 95 is dimensioned for transmission of energy of the frequency f4 of unit 25 and higher frequencies; wave guide 97, 99 is arranged for the transmission of energy of the frequency fs of unit 27 and higher frequencies; and wave guide 101, 103 is arranged t ture.

for the transmission of energy of the frequency of radar unit 29. The uppermost wave guide section 105, 107 is cut off for even the highest frequency, i. e. fs produced by radar unit 29.

As for energy of the frequency of radar unit 19, this energy is guided vertically upward in the several wave guides formed by wall sections 81, 83 and similar wall sections of the additional wave guide units, as far as the diagonal plane corresponding to the step 41 in the side -of the wave guide unit 63 and the similar steps in the other wave guide walls. As this energy cannot be propagated further upward within these wave guides, it is reilected as though from an inclined planar metallic reflector sheet positioned with its edge at 41, and hence the energy from unit 19 is directed in a substantially horizontal directive lobe, as indicated schematically at 119 in Fig. 1. The energy from unit 21, being of slightly higher frequency, is propagated upward eillciently through wave guide section 81, 83 and wave guide section 35, 87 as well, but is rejected by wave guide section 89, 91, because, as previously stated, this section is so dimensioned as to be cut off for this frequency. Accordingly, the energy generated by unit 21 is effectively reflected as though from a planar metallic sheet inclined at the angle of the step or junction 43 between metallic sheet sections and 89. Since this effective rellecting plane is inclined at a higher angle than the effective rellecting plane for radar unit 19, the directive lobe 121 associated with radar unit 21 is similarly provided at a higher angle, this angle of elevation of lobey 121 being higher than that of lobe 119 by an angle substantially twice as great as the angle between step 41 and step 43.

In a similar manner, the energy components of radar units 23, 25, 27 and 29 travel still further upward in unit 49 to produce energy transmission lobes 123, 125, 127 and 129, respectively. The same directive patterns apply to energy reflected back from distant objects, such energy being selectively received in the receiver sections of the respective radar units, according to the frequency. Each of the radar transmitter-receiver units may be provided with a conventional indicator such as a P. P. I. type cathode ray indicator for indicating the azimuthal direction and the distance of objects at the respective angles of elevation corresponding to their respective directive beams.

For some applications, it may be preferable to provide smoothly tapered interior dimensions in the wave guide array reflector system, instead of steps as illustrated in Figs. 1 and 2. In this event, the front elevation View of the smoothly tapered system 40 appears as shown in Fig. 3, the bottom dimensions of the system remaining as in the structures of Figs. 1 and 2, and the side elevation view remaining as in Fig. l, with the exception that no discrete lines 43, 45, 47, 49 and 51 appear in this struc- As before, parallel lower side sections 81 and 83 are provided. Above these are provided inclined metal sections 131 and 133 in wave guide unit 63', and similar inclined metal sections are provided in the other wave guide units. These inclined walls are warped in such a way as to dene rectangular cross-sectional regions at successively higher angles of inclination corresponding to the critical H-vector dimension for wave guides for the successively higher frequencies, in the same general manner as provided at the discrete steps in Figs. 1 and 2.

By way of illustration of a continuous-scan version of the present invention, particularly applicable to the multiple wave guide embodiment with smoothly tapered wave guide walls, Fig. 3 shows the antenna unit 11, 13 coupled to a single radar transmitter-receiver unit provided for periodic synchronized frequency sweeps of the transmitter and receiver tuning units. Such sweeps may be accomplished in electronic tuning circuits in a well known manner, or they may be accomplished electromechanically. The latter provision is schematically indicated in Fig. 3, with a frequency scan tuning system comprising a synchronous motor 134 coupled to the transmitter and receiver tuning controls, and supplied by power from an alternating current source 132'. Anindicator 135 1s provided, coupled to unit'130 and synchronized wlth units 134 and 132 for displaying target indications 1n coordinates of slant range and angle of elevation, a type of display known as type .E.V

If desired, the system 41B and the antenna and wave guide unit 13, may be arranged for rotation as a unit about a selected axis, e. g. the vertical axis as in Fig. 1. A rotatable joint coupling unit 16 is provided in wave guide 15 below reflector 11to permit angular movement. Y

A further modification whichV may be made in carrying out the principles of the present invention is the provision of curved steps in the construction of the array of wave guides side by side, the curves of the steps being preferably arranged-accordingto parabolic sections in such a manner as to provide collimation ofthe energy arriving at a given cut-off Aregion in the wave guide. A structure of this sort is Villustrated in Fig. 4 as including an exciter It will be readily apparent that many changes could be made without departing from the principles of the invention, as for example by departure from symmetry of each of the Wave guide units about a median plane, or by enclosure ofV any of themultiple wave guide reflector units by the attachment of a bottom plate and a frontal plate of dielectric material such as polystyrene, or-by modification of the frontal contours of the wave Vguide walls as by inclination or curvature thereof, to incorporate some refractive modification in the operation of the system.

, Thereflector unit 40 of Figs. l and 2 is illustrated in Fig. .2 as comprising only seven wave guide units placed side by side, and the steps in the internal width dimensions of each wave guide unit are illustrated as relatively large in order to bring out clearly the structure and operating principles of the invention. In practice, however,

system which may comprise a dipole element 113 and a Y the locus of the foci of the several parabolic reflector steps 141, 143, 145 and 147 and the corresponding steps of the wave guide units positioned alongside the unit seen in Fig. 4. The successive ones of these parabolic steps 141, 143, 145 and 147 have directive axes (directrices of the parabolas)` at successively higher angles of inclination, so that they produce a fan-shaped array of directive lobes, substantially similar to those illustrated in Fig. l..-

One practical type of mechanical construction which may be used in providing refiector-units such as reliector unit in Fig. 2 or reflector unit 140 in Fig. 4 is the provision of sectionally laminatedside walls in the reilector units, the inner laminations in each wave guide unit being produced with edges conforming to the desired reecting plane. Thus, a side wall for one of the wave guide units of the reflector system 140 comprises a rigid outer metallic side wall having an outline corresponding to the overall outline of unit 140 as seen in Fig. 4. The next layer comprises a second metallic sheet having curvilinear borders conforming to parabolic step 147 and the parabolic rear surface 149, and two straight-line borders ab and cd. The third layer comprises a still smaller sheet of relatively thin metal having curvilinear borders at 14S, 149; the fourth layer is a sheet having-curvilinear borders at 143 and 149, and the innermost sheet of the laminated side wall having curvilinear borders at 141 and 149. The outer'walls are built to close tolerance, and the inner laminations are of thin sheet metal bonded together with complete adhesion therebetween. It is thus possible to construct an antenna system for which small changes of frequency are adequate to produce appreciable changes of direc- `tivity, and `in Which the dimensions are predetermined with great accuracy.

A system as shown in Fig. 4 may be arranged for rotation about a vertical axis in a manner generally similar to that indicated yin Fig. Vl, but with the cylindrical parabolic reflector unit 111 and the dipole feeder unit 113 rigidly positioned with respectto the multiple wave guide reflector system 140 and arranged to be rotated therewith. Y

the extent of thesteps ordinarily is quite small, and furthermore, the Wave guide units ordinarily will appear considerably narrower than reference to Figs. 2 and 3 would indicate. For a paraboloidal reflector 11 (Fig. 1) of the size designed to produce a directive pattern of the order of 5 cone angle (with reference to the half-power points in the directive pattern), the reflector unit 40 may comprise thirty to fifty narrow wave guide units, rather than the seven units which appear with exaggerated breadths in Fig. 2. These comments apply equally to the structures shown in Figs. 3 and 4.

Fig. 5 illustrates a modification of the system shown in Fig. 4, wherein the cylindrical parabolic reflector 111 is eliminated, and the lower edges of the Wave guide walls are cut for slightly different downward projections conforming to a lens which may be of the cylindrical electromagnetic lens type. This lens produces planar-beam collimation of the energy corresponding to that produced in Fig. 4 by reflector 111.

Where a wave guide array such as illustrated in Fig. 5 is employed, the exciter unit may comprise a dipole element 171fed as by a coaxial line 173. A further dipole reliector element 175 may be provided, if desired, for conservation of the energy and for generally directing the energy into the entry lens formed in the lower part of the multiple wave guide array. As before, the dipole element 171 is oriented in a plane parallel with the wave guide walls, so that the E vector of the energy supplied to the wave guide system lies parallel with the walls and the H vector lies in the direction substantially perpendicular to the wall surfaces. Thus, the critical wave guide dimension is made to be the spacing dimension or separation between the interior wall surfaces at any point in the wave guides.

If desired, the lower edges of the metallic sheets employed in the wave guide array maybe cut and arranged as a 4full Fresnellens, as illustrated in Fig. 6, for achieving collimation of energy arriving from a substantially point-source radiator such-as the dipole 171 at the lens focal point. With such an arrangement, full collimation is achieved, corresponding to that provided by the paraboloidal refiector 11 in Fig. 1, but with the reflector element eliminated.

It will be readily apparent that if the antenna system of Fig. 4, Fig. 5 or Fig. 6 is to be rotated, as in a longrange azimuthal system of the general type illustrated in Fig. l, the multiple wave guide array and the exciting antenna unit normally are arranged to be kept in fixed relative positions, and the entire structure is rotated about the vertical axis, With the provision of a suitable axially aligned wave guide or coaxial feed line and with a rotatable joint or coupling employed therein.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A microwave energy directing system comprising a wave guide having a pair of conductive walls spaced apart by an extent small compared with the dimensions in the walls, and means for introducing microwave energy between said walls for propagation along the space therebetween, said energy introducing means comprising means for introducing energy components of different frequencies within a predetermined range of frequencies, and said wave guide having `an energy entrance section eficiently transmitting substantially all energy frequencies in said predetermined range, and sections progressively farther from said energy entrance section cutting off energy transmission of progressively higher frequencies in said predetermined range, said sections being angularly disposed relative to each other, said wave guide being closed in its section farthest from said energy entrance section for preventing entrance or escape of energy therethrough, and being open at said energy entrance section for directional radiation of microwave energy reflected from the interior thereof.

2. A microwave energy directing system comprising a wave guide having la pair of conductive walls spaced apart by an extent small compared with the dimensions in thY walls, and means for introducing microwave energy between said walls for propagation along the space therebetween, said energy introducing means comprising means for introducing energy components of different frequencies within a predetermined range of frequencies, and said wave guide having an energy entrance section efficiently transmitting substantially all energy frequencies in said predetermined range, and sections progressively farther from said energy entrance section cutting off energy transmission of progressively higher frequencies in said predetermined range, rectangular cross-sectional areas being bounded between said conductive wa'lls, the widths of the cross-sectional interior rectangles being progressively narrower at progressively greater distances from said energy entrance section, said :rectangular cross-sectional areas being at mutual angular dispositions, whereby energy components of different frequencies in said predetermined range are reflected from non-parallel reflecting regions in said wave guide.

3. A microwave energy directing system as defined in claim l, wherein the spacing dimension between said walls is progressively smaller at progressively greater distances from said energy entrance section.

4. A microwave energy directing system as defined in claim l, wherein said walls have first corresponding parallel areas of a maximum spacing or separation, and corresponding further parallel areas of a smaller spacing or separation, at least one of said walls having an abrupt step between the first `area and the further area therein.

5. Microwave energy directing apparatus comprising a wave guide having a pailr of conductive interior walls separated by a maximum distance small compared to the outline dimensions of said walls, said wave guide having an energy entrance section of maximum separation between the interior walls and having a section of minimum spacing between the interior walls, the separation between the interior walls being progressively smaller at progressively greater distances from said energy entrance section, the interior surface of at least one of said walls comprising a series of planar sections with steps therebetween, said sections being substantially parallel to the corresponding sections of the opposite wall, said planar sections being trapezoidal in shape, and the steps therebetween being formed along straight lines angularly disposed in said wall.

6. Microwave energy directing apparatus comprising a wave guide having a pair of conductive interior walls separated by a maximum distance small compared to the outline dimensions of said walls, said wave guide having an energy entrance section of maximum separation between the interior walls and having a section of minimum spacing between the interior walls, the separation between the interior walls being progressively smaller at progressively greater distances from said energy entrance section, the interior surface of at least one of said walls Comprising a series of planar sections with steps therebetween, said planar sections having curved borders and said steps accordingly being along curvilinear locations in the wall.

7. An antenna system comprising means for producing a collimated beam of microwave energy directed along an axis and having a cross-sectional area of several waveengths minimum dimension, and a beam bending wave guide array having an energy entrance grid positioned transverse said axis receiving said collimated beam and an energy exit grid angularly positioned relative to said entrance grid, the wave guides of said array having identical interior congurations with corresponding parts thereof in alignment, each of said wave guides having a pair of conductive interior walls separated by a maximum distance small compared to the outline dimensions of said walls, each of said wave guides having a section of minimum spacing between the interior walls, means in the sections of minimum separation between the interior walls for preventing passage of energy therethrough between the interiors of said wave gui es and the space therebeyond, the separation between the pair of interior walls of each wave guide being progressively smaller at progressively greater distances from said energy entrance grid.

8. An antenna system as defined in claim 7, wherein said means for producing a collimated beam of microwave energy comprises means for fixing the electric lines of force in said beam parallel with the entrance grid walls of said wave guides.

9. An antenna system as defined in claim 8, further including means rotating said beam bending wave guide array and said means for fixing the electric lines of force parallel with the entrance grid walls of said wave guides about said collimated beam axis.

10. An antenna system comprising a beam bending wave guide array including a plurality of wave guides in side-by-side positional relation, the wave guides of said array having interior configurations with corresponding parts thereof in alignment, each of said wave guides having a pair of conductive interior walls separated by a maximum distance small compared to the outline dimensions of said walls, said maximum separation being along an energy entrance border of each wave guide, each of said wave guides having a section of minimum spacing between the pair of interior walls, means in the sections of minimum separation between the interior walls for preventing passage of energy therethrough between the interiors of said wave guides and the space therebeyond, the separation between the pair of interior walls of each wave guide being progressively smaller at progressively greater distances from said energy entrance borders; said system comprising also means for directing microwave energy into said entrance borders of said wave guides and thence toward said sections of minimum spacing and polarizing said energy with its electric lines of force substantially parallel with said walls, said last named means including means for distributing the energy among the wave guides of said array for emergence of a concentrated directive energy beam from said array.

1l. An antenna system as defined in claim l0, wherein said means for preventing passage of energy between the interiors of said wave guides and the space therebeyond comprises means for conducting currents between the walls of said wave guides at said section of minimum spacing therebetween.

l2. An antenna system comprising a beam bending wave guide array including a plurality of substantially identical wave guides in side-by-side positional relation,

the wave guides of said array having identical interior configurations with corresponding parts thereof in alignment, each of said wave guides having a pair of conductive interior walls separated by a maximum distance small compared to the outline dimensions of said walls, said maximum separation being along an energy entrance border of each wave guide, each of said Wave guides having a section of minimum spacing between the pair of interior walls, the separation between the pair of interior walls of each wave guide being progressively smaller at progressively greater distances from said energy entrance borders; said system comprising also means for directing microwave energy into said entrance borders of said Wave guides and polarizing said energy with its electric lines of force substantially parallel with said walls, said last-named means including means for distributing the energy components among the wave guides of said array for emergence of a concentrated directive energy beam from said array, said interior walls being formed with substantially parabolic contours of uniform spacing therebetween in each wave guide, and said means for directing microwave energy into said entrance borders comprising an antenna unit with a narrow effective aperture dimension in the direction parallel with its electric vector and with an elongated direction perpendicular thereto and parallel to the direction of alignment of corresponding parts of said wave guides in said array.

13. An antenna system as defined in claim 12, wherein said antenna unit comprises a cylindrical parabolic reflector with close-spaced parallel end walls forming, with the ends of the reflector, a long narrow rectangular energy emergence opening, said antenna unit being positioned with said reiiector directed toward the wave guides in the middle of said array and with said rectangular emergence opening extending along the region of the foci of said parabolic contours.

14. An antenna system comprising a beam bending Wave guide array including a plurality of substantially identical wave guides in side-by-side positional relation, the wave guides of said array having identical interior configurations with corresponding parts thereof in Valignment, each of said wave guides having a pair of conductive interior walls separated by a maximum distance small compared to the outline dimensions of said walls, said, maximum separation being along an energy entrance border of each wave guide, each of said Wave guides having a section of minimum spacing between the pair of interior walls, the separation between the pair of interior walls of each wave guide being progressively smaller at progressively greater distances from said energy entrance borders; said system comprising also means for directing microwave energy into said entrance borders of said wave guides and polarizing said energy with its electric lines of force substantially parallel with said Walls, said last-named means including means for distributing the energy components among the wave guides of said array for emergence of a concentrated directive energy beam from said array, said Vinterior walls being formed with substantially rectilinear loci of uniform spacing therebetween in each Wave guide, the lines of one spacing being at an acute angle to the lines of another spacing in each wave guide; and said means for directing microwave energy into said entrance borders comprising means for collimating said energy into a compact beam in both the E plane and the H plane of the energy waves entering said wave guide array.

15. An antenna system as defined in claim 10, wherein `the energy entrance borders of said wave guides conform 10 to the contours of a wave guide lens for collimating the microwave energy as it enters said array.

16. An antenna system as defined in claim 10, wherein Vthe energy entrance borders of said wave guides conform to the contours of a cylindrical lens for collimating the energy in one place, and the interior walls of the wave guides are formed with substantially parabolic contours of uniform spacing therebetween in each wave guide for reiiecting selected frequency components of the energy and completing their collimation.

17. An antenna system as defined -in claim 10, wherein said interior walis are formed with substantially rectilinear loci of uniform spacing therebetween in each wave guide, the lines of one spacing therebetween being at an acuate angle to the lines of another spacing in each wave guide; and wherein the energy entrance borders of said wave guide conform to the contours of a wave guide lens for collimating the microwave energy into-a pencil beam as it enters said wave guide array.

18. A microwave energy directive system comprising a wave guide having a pair of spaced walls, said wave guidehaving an energy entrance section efficiently transmitting all energy frequencies within a predetermined range and sections progressively farther from said entrance section cutting off energy at successively higher frequencies within said range, the junction between successive sections defining a reflecting plane for energy below the cut-off frequency, said reiiecting planes being angularly disposed relative to each other whereby the energy beam reflected at each plane is angularly disposed with respect to the energy beam reflected from each of the other planes.

19. A microwave energy directive system comprising a wave guide having a pair of spaced walls, said wave guide having an energy entrance section and energy exit section which efficiently transmit all energy frequencies within a predetermined range, said sections being angularly disposed relative to each other, said Walls being parallel at the entrance and exit sections and converging inwardly from said sections, the walls converging at a greater angle adjacent the entrance section than the exit section whereby a plurality of reiiecting planes taken perpendicular to the parallel portions of the walls and having parallel edges at the intersection of the reflecting planes and the converging portion of the walls are angularly disposed relative to each other.

20. A microwave energy directive system comprising a wave guide having a pair of spaced walls, said wave guide having an energy entrance section and energy exit section which eiciently transmit all energy frequencies within a predetermined range, said sections being angularly disposed relative to each other, said walls being parallel at the entrance and exit sections and converging inwardly from said sections for reecting energy.

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